U.S. patent number 11,435,407 [Application Number 16/631,047] was granted by the patent office on 2022-09-06 for device and method for enhancing accuracy of detecting leakage current.
The grantee listed for this patent is Hyun Chang Lee. Invention is credited to Hyun Chang Lee.
United States Patent |
11,435,407 |
Lee |
September 6, 2022 |
Device and method for enhancing accuracy of detecting leakage
current
Abstract
The device for detecting a leak may include: an earth voltage
measuring unit measuring earth voltage; an ADC unit sampling the
measured earth voltage and converting the sampled earth voltage
into a digital value; an effective value calculating unit
calculating an effective value of the earth voltage converted into
the digital value; a Fourier transforming unit performing Fourier
transform of the measured earth voltage to calculate voltage for
each harmonic component; a content rate calculating unit
calculating a voltage content rate of the fundamental frequency to
voltage; a harmonic distortion rate calculating unit calculating a
total harmonic distortion and a harmonic distortion factor based on
the voltage for each harmonic component; a zero-crossing estimating
unit estimating a zero-crossing count; and a suspicious earth
leaking area determining unit determining that the earth voltage is
generated by the leak of the AC commercial power.
Inventors: |
Lee; Hyun Chang (Gyeonggi-do,
KR) |
Applicant: |
Name |
City |
State |
Country |
Type |
Lee; Hyun Chang |
Gyeonggi-do |
N/A |
KR |
|
|
Family
ID: |
1000006543454 |
Appl.
No.: |
16/631,047 |
Filed: |
April 6, 2018 |
PCT
Filed: |
April 06, 2018 |
PCT No.: |
PCT/KR2018/004066 |
371(c)(1),(2),(4) Date: |
January 14, 2020 |
PCT
Pub. No.: |
WO2019/017568 |
PCT
Pub. Date: |
January 24, 2019 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20200150189 A1 |
May 14, 2020 |
|
Foreign Application Priority Data
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Jul 19, 2017 [KR] |
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10-2017-0091665 |
Aug 1, 2017 [KR] |
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10-2017-0097857 |
Mar 6, 2018 [KR] |
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10-2018-0026207 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01R
31/083 (20130101); G01R 19/2513 (20130101); G01R
23/20 (20130101); G01R 19/2509 (20130101); G01R
21/133 (20130101); G01R 31/50 (20200101); G01R
23/02 (20130101) |
Current International
Class: |
G01R
31/50 (20200101); G01R 23/20 (20060101); G01R
23/02 (20060101); G01R 21/133 (20060101); G01R
19/25 (20060101); G01R 31/08 (20200101) |
Field of
Search: |
;702/75 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2010190645 |
|
Sep 2010 |
|
JP |
|
100503713 |
|
Jul 2005 |
|
KR |
|
1020150059103 |
|
May 2015 |
|
KR |
|
1020150131395 |
|
Nov 2015 |
|
KR |
|
1020170007696 |
|
Jan 2017 |
|
KR |
|
Primary Examiner: Le; John H
Attorney, Agent or Firm: Park; Nicholas
Claims
The invention claimed is:
1. A device for detecting a leak, the device comprising: an earth
voltage measuring unit measuring earth voltage; an ADC unit
sampling the measured earth voltage and converting the sampled
earth voltage into a digital value; an effective value calculating
unit calculating an effective value of the earth voltage converted
into the digital value; a Fourier transforming unit performing
Fourier transform of the measured earth voltage to calculate
voltage for each harmonic component which is an integer multiple of
a fundamental frequency, based on the effective value of the earth
voltage; a content rate calculating unit calculating a voltage
content rate of the fundamental frequency to the voltage obtained
by adding the voltage for each harmonic component based on the
voltage for each harmonic component; a harmonic distortion rate
calculating unit calculating a total harmonic distortion and a
harmonic distortion factor based on the voltage value for each
harmonic component; a zero-crossing estimating unit estimating a
zero-crossing count at which the earth voltage converted into the
digital value passes through zero voltage for a predetermined time
T1; and a suspicious earth leaking area determining unit
determining that the earth voltage is generated by the leak of the
AC commercial power based on at least any one of the effective
value of the earth voltage, the voltage content rate, the total
harmonic distortion, the harmonic distortion factor, the
zero-crossing count, and the distortion count and determining a
region where the earth voltage is measured as the suspicious earth
leaking area based on the determination result.
2. The device of claim 1, wherein the predetermined time T1 is a
time which is a predetermined integer multiple of a cycle of the AC
commercial power.
3. The device of claim 1, further comprising: a distortion
estimating unit estimating the distortion count which is the number
of times at which the distortion by the harmonics occurs in the
measured earth voltage for the predetermined time T1, wherein the
suspicious earth leaking area determining unit determines the
suspicious earth leaking area based on at least any one of the
effective value of the earth voltage, the voltage content rate, the
total harmonic distortion, the harmonic distortion factor, the
zero-crossing count, and the distortion count.
4. The device of claim 3, wherein when a polarity of a first change
amount of a digital value of first earth voltage converted through
sampling and a digital value of second earth voltage converted
through sampling after a next sampling period and the polarity of a
second change amount of a digital value of the second earth voltage
and a digital value of third earth voltage converted through
sampling after a next sampling period are different from each
other, the distortion estimating unit determines that the
distortion by the harmonics occurs to estimate the distortion
count.
5. The device of claim 3, wherein the suspicious earth leaking area
determining unit determines that the earth voltage is generated by
the leak of the AC commercial power when the effective value of the
earth voltage exceeds a predetermined threshold voltage value, the
voltage content rate exceeds a predetermined voltage content rate,
the total harmonic distortion is less than a predetermined total
harmonic distortion, the harmonic distortion factor is less than a
predetermined harmonic distortion factor, the zero-crossing count
coincides with a predetermined count, and the distortion count is
less than a predetermined count.
6. The device of claim 1, wherein the earth voltage measuring unit
includes an electrode connected with a measurement point A which is
a predetermined point on a ground surface, an electrode connected
with a measurement point B which is a predetermined point on the
ground surface, which is different from the measurement point a, a
resistance array connected between the measurement point A and the
measurement point B in parallel, and a voltage measuring unit
measuring voltage between both ends of the resistance array.
7. The device of claim 1, wherein the zero-crossing estimating unit
estimates the zero-crossing count passing through the zero voltage
when the polarity of the earth voltage is changed for the
predetermined time T1.
8. The device of claim 1, wherein the suspicious earth leaking area
determining unit determines that the earth voltage is generated by
the leak of the AC commercial power when the effective value of the
earth voltage exceeds a predetermined threshold voltage value, the
voltage content rate exceeds a predetermined voltage content rate,
the total harmonic distortion is less than a predetermined total
harmonic distortion, the harmonic distortion factor is less than a
predetermined harmonic distortion factor, and the zero-crossing
count coincides with a predetermined count.
9. The device of claim 1, further comprising: a magnetic field
signal receiving unit receiving a magnetic field signal generated
from an exploration current generating device; a leak detection
voltage signal receiving unit receiving a leak detection voltage
signal generated from a leak detection voltage signal generating
device; a power line buried path search unit searching a path of a
power line buried in the suspicious earth leaking area based on the
magnetic field signal; and a leak point determining unit
determining a leak point of the buried power line based on the leak
detection voltage signal.
10. The device of claim 9, wherein the leak point determining unit
sets a logical value according to whether to receive the leak
detection voltage signal and determines a point where the set
logical value and a logical value of the leak detection voltage
signal generated by the leak detection voltage signal generating
device coincide with each other and the magnitude of the leak
detection voltage signal has a maximum value as the leak point.
Description
TECHNICAL FIELD
The present disclosure relates to an electric power field, and more
particularly, to a device and a method for improving the accuracy
of earth leakage detection.
BACKGROUND ART
A device and a method for determining whether the occurrence of
earth leakage and locating an earth leaking point in a multi-common
grounding environment by a ground fault (earth leakage) of a power
line buried in the ground have been disclosed.
There are Korean Patent No. 10-1559533 disclosing "Mobile Apparatus
and Method For Locating Earth Leaking Point", Korean Patent
Publication No. 10-2017-0007696 disclosing "The apparatus and
method to locate the leaking point efficiently under TN-C
environment", and as a non-patent document, new power technology
No. 104 disclosing "Low Voltage Line Path and Leak Detection
Technology in Neutral Line Common Grounding Environment".
DISCLOSURE
Technical Problem
Electric power companies are required to ground a neutral point of
the power source (transformer) to the earth to detect a defect that
is caused by a ground fault (electrical leakage) which accounts for
most of the power equipment failure and leaks out a dangerous
voltage from inside through an insulation degraded point to the
surrounding soil (earth). In the event of a ground fault, a
returning fault current from the earth to the grounded neutral
point of the power source (transformer) is continuously monitored
to detect the occurrence of a ground fault, and further action to
clear the cause of the fault. In other words, the non-faulty return
current of unbalanced load returns to the neutral point of power
source (transformer) through a neutral line, while the ground fault
(earth leak) current returns through the earth, respectively.
However, when the earth leakage fault is located at a distance far
from the power source (transformer), earth resistance increases to
block the fault (leak) current from reaching the grounded neutral
point of the power source. And as a result, it is impossible to
detect the leak fault at a power source, and the power is
continuously supplied without any protective measures so that a
risk of an electric shock accident may increase.
In order to prevent the risk of the electric shock by earth
resistance according to the distance between the power source and
the earth leaking point, a multi-common grounding method (MEN,
Multiple Earthed Neutral) is introduced, which grounds a neutral
line at various points in the middle of a power line according to
the regulations such as IEC60364. Previously only one point of the
power source (transformer) is grounded but now multiple locations
of the power line (neutral line) which one grounded point of the
power source is extended are grounded to the earth and the return
distance of fault (leak) current is shortened to minimize an
influence by the earth resistance, thereby preventing the electric
shock accident.
However, if the neutral line is grounded at multiple locations
configured as MEN in the power system, a closed circuit (ground
loop) is formed between the neutral groundings, and both return
currents regardless of its origin, non-fault (unbalanced load) or
fault, can flow either path freely and circulate in the loop. The
mixed circulating current can cause the malfunction when
identifying the fault current and locating the suspicious earth
leaking area by measuring the vector sum of the current flowing in
the power line
In order to solve such a problem, in the related art, the
conventional technique detects whether an occurrence of earth
leaking and locates a suspicious earth leaking area as depicted in
FIG. 1 by measuring the earth potential rather than measuring the
returning or the vector summing current to determine a suspicious
earth leaking area at the location of earth potential raised by the
earth leaking and then determines the location of the earth leaking
point by detecting an exploration signal after injecting the signal
into the power cable in a suspicious area.
FIG. 1 is a flowchart of the task of locating an earth leakage
point by measuring an earth voltage used in the related art. The
task includes acquiring a ground voltage (V1) by measuring the
earth potential between a ground point and another ground point or
a neutral line (not illustrated) that is connected to the ground
point in adjacent customer premises and then analyzing the V1 to
determine a suspicious earth leaking area where the V1 has voltage
level more than threshold (103), the content rate which is
indicating the ratio of the power frequency component (VF) equal or
more a certain level and the variation rate of V1 is within a
specific range while the internal resistance changes (105). And
locating an earth leaking point in the suspicious earth leaking
area (106) by connecting a leak exploration signal generating
device to a power line in the suspicious earth leaking area (107),
moving along a buried path of the power line (108 and 109), and
detecting the exploration signal from the earth surface (113)
injected by the exploration signal generating device by using a
leak detection device (110, 111, and 112).
FIG. 2 illustrates a front end circuit and an internal algorithm
configuration of a leak detecting device for executing two separate
tasks depicted in FIG. 1. To find a suspicious earth leaking area
102, an earth voltage (V1,122) and power frequency (50 or 60 Hz)
voltage (Vf) of input impedance 119 between an earth leaking
predicted point 117 and remote ground 118 or between neutral line
of customer premises which is near earth leaking predicted point
117 and a remote ground 118 is measured and then the content ratio
may be obtained by applying the ratio of the earth voltage (V1) and
the power frequency (50 or 60 Hz) voltage (Vf) to [Equation 1].
Also, the variation rate may be calculated by varying the input
impedance 119 of the measuring circuit and applying the measured
voltage magnitude to [Equation 2]. Content rate=60 Hz component
voltage/total earth voltage*100 [Equation 1] Variation
rate=(voltage at maximum resistance)-(voltage at minimum
resistance)/voltage at minimum resistance*100 [Equation 2]
When it is found that the place is the suspected earth leaking area
based on the content rate and the rate of change, it is possible to
perform an earth leak point detection work to determine the
location of an earth leaking point in the area.
FIG. 3 shows a configuration of a device for detecting a leak point
in the suspicious earth leaking area. A leak detecting apparatus
1000 proceeds along a buried path of a power line 202 and 203 in
the suspicious earth leaking area by obtaining a radiated
electromagnetic pulse signal 111 and 112 when a current pulse
signal transmitted by a leak exploration signal generating
apparatuses 302, 303 flows through the power line 202, 203,
measures an earth voltage 212 by contacting the land surface 105,
106 of the buried path. Further, the leak detecting apparatus 1000
detects a voltage pulse signal 110 included in the earth voltage
211 from the earth at a signal generation time notified by the
magnetic field pulse signals 111 and 112. The voltage pulse signal
110 is designed to generate a next signal 110 at a predetermined
interval from the time at which the magnetic field pulse signals
111 and 112 are received so that the leak detecting device 1000
detects a signal included in the earth voltage at a generation time
of the next signal 110 and determines a maximum point of the signal
as the leak point 128.
As described above, a technique has been used in the field to
detect a leak voltage pulse signal 140 contained in the earth
voltage on the ground surface within the suspicious earth leaking
area and determine the location of leak source regardless of
whether the neutral line is grounded in multiple or single
location(s). But as illustrated in FIG. 4, a magnetic field
generated due to alternating current 153 flowing on an electric
wire 151 corresponds to magnetic field induction 155 formed by an
adjacent conductor 152 to cause a magnetic field coupling 154
phenomenon. Further, the electric wire 151 causes the electrostatic
coupling 157 by an electrostatic induction 158 phenomenon of the
adjacent conductor 152. That is, when the earth potential is raised
by induced voltage generated by the magnetic field coupling 154 and
the electrostatic coupling 157 and/or stray voltage generated when
unbalanced load return current which flows on a multi-ground
neutral line flows out to the earth through a ground point, an
error that the case is determined as if the actual leak occurrence
as illustrated in FIG. 5.
In the related art, in order to distinguish between an actual leak
in which risk voltage flows out to the ground due to an insulation
failure of a power facility transmitting or storing AC commercial
power and a rise in earth potential due to the induced voltage or
the stray voltage which is parasitic around the power line, the
actual leak and the rise in earth potential are intended to be
distinguished by measuring the content rate and the voltage
variation rate in the earth voltage (V1), but when this is applied
in the field, the actual leak and the rise in earth potential
cannot be accurately distinguished, and an error in which the
location of the parasitic voltage source around the power line is
detected as the location of actual leak occurs as in FIG. 5.
In order to solve the problem mentioned above, it is necessary to
propose a method and a device for correctly distinguishing the
actual leak source and the earth potential rise by the induced or
stray voltage source, which is continuously parasitic around the
power line.
Technical Solution
An embodiment of the present disclosure provides a device for
detecting an earth leakage. The device for detecting an earth
leakage may include: an earth voltage measuring unit measuring
earth voltage; an ADC unit sampling the measured earth voltage and
converting the sampled earth voltage into a digital value; an
effective value calculating unit calculating an effective value of
the earth voltage converted into the digital value; a Fourier
transforming unit performing Fourier transform of the measured
earth voltage to calculate a voltage for each harmonic component
which is an integer multiple of a fundamental frequency--a utility
frequency of AC commercial power--, based on the effective value of
the earth voltage; a content rate calculating unit calculating a
voltage content rate of the fundamental frequency to the voltage
obtained by adding the voltage for each harmonic component based on
the voltage for each harmonic component; a harmonic distortion rate
calculating unit calculating a total harmonic distortion and a
harmonic distortion factor based on the voltage for each harmonic
component; a zero-crossing estimating unit estimating a
zero-crossing count at which the earth voltage converted into the
digital value passes through zero voltage for a predetermined time
T1; and a suspicious earth leaking area determining unit
determining a suspicious earth leaking area where the earth voltage
is generated by the leak of the AC commercial power based on at
least any one of the effective value of the earth voltage, the
voltage content rate, the total harmonic distortion, the harmonic
distortion factor, and the zero-crossing count.
The predetermined time T1 may be a time which is a predetermined
integer multiple of a cycle of the AC commercial power.
In addition, the device may further include a distortion estimating
unit estimating the distortion count which is the number of times
the distortion by the harmonics occurs in the measured earth
voltage for the predetermined time T1 and the suspicious earth
leaking area determining unit may determine the suspicious earth
leaking area based on at least any one of the effective value of
the earth voltage, the voltage content rate, the total harmonic
distortion, the harmonic distortion factor, the zero-crossing
count, and the distortion count.
The distortion estimating unit may detect the first polarity of
change by comparing a digital value of the first earth voltage
converted through sampling and a digital value of the second earth
voltage converted through a next sampling period. In the same
manner, the distortion estimating unit detects the second polarity
of change by comparing a digital value of the second earth voltage
converted through sampling and a digital value of the third earth
voltage converted through a succeeding sampling period. When the
distortion estimating unit finds that the first polarity and the
second polarity are changed, the distortion estimating unit may
determine that the distortion by the harmonics occurs and increase
the distortion count.
Further, the earth voltage measuring unit may include an electrode
connected with a predetermined measurement point "a" on a ground
surface, an electrode connected with a predetermined measurement
point "b" differs from the point "a" on the ground surface, a
resistance array connected in parallel between the measurement
point "a" and "b", and a measuring unit which measures a voltage
between both ends of the resistance array.
In addition, the zero-crossing estimating unit may count the number
of zero-crossings that cross the zero voltage at the same time the
polarity of the earth voltage is changed during the predetermined
time T1.
Moreover, the suspicious earth leaking area determining unit may
determine that the earth voltage is generated by the leak of the AC
commercial power when the effective value of the earth voltage
exceeds a predetermined threshold voltage value, the voltage
content rate exceeds a predetermined voltage content rate, the
total harmonic distortion is less than a predetermined total
harmonic distortion, the harmonic distortion factor is less than a
predetermined harmonic distortion factor, and the zero-crossing
counts coincides with a predetermined count.
In addition, the suspicious earth leaking area determining unit may
determine that the earth voltage is generated by the leak of the AC
commercial power when the effective value of the earth voltage
exceeds a predetermined threshold voltage value, the voltage
content rate exceeds a predetermined voltage content rate, the
total harmonic distortion is less than a predetermined total
harmonic distortion, the harmonic distortion factor is less than a
predetermined harmonic distortion factor, the zero-crossing count
coincides with a predetermined count, and the distortion count is
less than a predetermined count.
Further, the device for detecting an earth leakage may further
include: a magnetic field signal receiving unit receiving a
magnetic field signal generated from an exploration current
generating device; a leak detection voltage signal receiving unit
receiving a leak detection voltage signal generated from a leak
detection voltage signal generating device; a power line buried
path search unit searching a path of a power line buried in the
suspicious earth leaking area based on the magnetic field signal;
and a leak point determining unit determining a leak point of the
buried power line based on the leak detection voltage signal.
The leak point determining unit may set a logical value according
to whether or not a leak detection voltage signal is received, and
the point at which the magnitude of the detection voltage signal
has the maximum value can be determined as the leakage current
point when all the logic value match the logic value of the leakage
detection voltage signal generated by the leakage detection voltage
signal generator.
Another embodiment of the present disclosure provides a method for
detecting a leak. The method for detecting leak may include:
measuring earth voltage; sampling the measured earth voltage and
converting the sampled earth voltage into a digital value;
calculating an effective value of the earth voltage converted into
the digital value; performing Fourier transform of the measured
earth voltage to calculate voltage for each harmonic component
which is an integer multiple of a fundamental frequency--a power
frequency of AC commercial power--, based on the effective value of
the earth voltage; calculating a voltage content rate of the
fundamental frequency to voltage obtained by adding the voltage for
each harmonic component based on the voltage for each harmonic
component; calculating a total harmonic distortion and a harmonic
distortion factor based on the voltage value for each harmonic
component; estimating a zero-crossing count at which the earth
voltage converted into the digital value passes through zero
voltage for a predetermined time T1; and determining that the earth
voltage is generated by the leak of the AC commercial power based
on at least any one of the effective value of the earth voltage,
the voltage content rate, the total harmonic distortion, the
harmonic distortion factor, and the zero-crossing count, and
determining a region where the earth voltage is measured as the
suspicious earth leaking area based on the determination
result.
Advantageous Effects
According to one embodiment of the present disclosure, any ground
voltages (leakage voltages) caused either by parasitic voltages
existing around commercial power equipment or insulation failures
that may cause an accident of human life and equipment may be
distinguished regardless of the configuration of the neutral
grounding system. It is possible to prevent the electric shock by
improving the accuracy of earth leakage detection by suggesting the
means and method to identify and distinguish the cause of the earth
potential rise.
Besides, other features and advantages of the present disclosure
may be newly determined through embodiments described below with
reference to the present disclosure.
DESCRIPTION OF DRAWINGS
FIG. 1 is a workflow diagram for leak detection in the related
art.
FIG. 2 is an internal configuration diagram of a leak detecting
device in the related art.
FIG. 3 is an installation configuration diagram of a leak
exploration signal device for exploring a leak point and the leak
detecting device.
FIG. 4 illustrates the generation of induced voltage by a power
line, and electrostatic and magnetic field coupling.
FIG. 5 describes that in the related art, rising of an earth
potential is mistaken as the true leak by parasitic voltage
(induced and stray voltage) around the power line.
FIG. 6 illustrates an actual example of an earth voltage waveform
at a place where the true leak occurs.
FIG. 7 illustrates an actual example of a waveform of earth
voltage, which rises by power line parasitic voltage.
FIG. 8 illustrates an actual example of the waveform of the earth
voltage, which rises by the power line parasitic voltage.
FIG. 9 is a spectrum for each waveform of earth voltage, which
rises by the true leak and frequency (harmonic) at the time of
Fourier transform.
FIG. 10 is a spectrum for each waveform of earth voltage, which
rises by the parasitic voltage and frequency (harmonic) at the time
of Fourier transform.
FIG. 11 illustrates the number of times a distortion count is
generated in the waveform of the earth voltage, which rises by the
parasitic voltage.
FIG. 12 illustrates a distortion count method in a distorted
waveform.
FIG. 13 is a workflow diagram for the distortion count illustrated
in FIG. 12.
FIG. 14 illustrates an exploration configuration of a portion where
the earth voltage rises by the true leak without transmission
(injection) of a separate leak exploration signal, that is, a
suspicious earth leaking area of the leak detecting device
1000.
FIG. 15 is a flowchart of the exploration work of the suspicious
earth leaking area of FIG. 14.
FIG. 16 illustrates a leak point detection configuration using a
leak detecting device after transmission (injection) of a leak
exploration signal to a power line located at an area determined as
the suspicious earth leaking area in FIG. 15.
FIG. 17 is a flowchart of the leak point exploration work of FIG.
16.
FIG. 18 describes that the portion where the earth potential rises
by the true leak, that is, the suspicious earth leaking area is
explored.
FIG. 19 describes that a leak point is explored in the suspicious
earth leaking area.
FIG. 20 illustrates an example of a screen displaying a result of
exploring the portion where the earth voltage rises by the true
leak without transmission (injection) of the separate leak
exploration signal.
FIG. 21 illustrates an example of a screen displaying a result of
Fourier-transform of the earth voltage of which potential rises by
the true leak in FIG. 20.
FIG. 22 illustrates an example of a screen showing the waveform of
the earth voltage of which potential rises by the true leak in FIG.
20.
FIG. 23 illustrates an example of a screen displaying a result of
transmitting (injecting) the leak exploration signal to the power
line in a corresponding area and exploring the leak point after
determining an area where the earth potential rises by the true
leak in FIG. 20 as the suspicious earth leaking area.
FIG. 24 illustrates an example of a screen displaying a result of
exploring the portion where the earth voltage rises by the
parasitic voltage without transmission (injection) of the separate
leak exploration signal.
FIG. 25 illustrates an example of a screen displaying a result of
Fourier-transform of the earth voltage of which potential rises by
the parasitic voltage in FIG. 24.
FIG. 26 illustrates an example of a screen showing the waveform of
the earth voltage of which potential rises by the parasitic voltage
in FIG. 24.
FIG. 27 illustrates an example of a screen displaying a result of
transmitting (injecting) the leak exploration signal to the power
line and exploring the leak point in order to check whether the
portion is misdetermined as a suspicious earth leaking area even
though the portion where the earth potential rises by the parasitic
voltage is not determined as the suspicious earth leaking area in
FIG. 24.
FIG. 28 is an example of a ZCC/DC function selection screen for
determining waveform distortion.
FIG. 29 is a block diagram of a leak detecting device according to
another embodiment of the present disclosure.
FIG. 30 illustrates an example for describing a method for
measuring earth voltage in another embodiment of the present
disclosure.
FIG. 31 illustrates an example for describing a method for
calculating the number of distortion times according to another
embodiment of the present disclosure.
FIG. 32 is a flowchart for the method for calculating the number of
distortion times according to another embodiment of the present
disclosure.
FIG. 33 is an explanatory diagram of a protocol for receiving a
magnetic field signal and receiving a leak detection voltage signal
according to another embodiment of the present disclosure.
FIG. 34 illustrates an example showing a relationship between a
start time notification by the leak detection voltage signal and a
time when the leak detection voltage signal is measured according
to another embodiment of the present disclosure.
FIG. 35 is a flowchart for a method for determining another
suspicious earth leaking area according to another embodiment of
the present disclosure.
FIG. 36 is a flowchart for a method for determining a leak point
according to another embodiment of the present disclosure.
DETAILED DESCRIPTION
Various embodiments will now be described with reference to
drawings and like reference numerals are used to refer to like
elements throughout all drawings. In the present specification,
various descriptions are presented to provide an appreciation of
the present disclosure. However, the embodiments can be executed
without a specific description. In other examples, known structures
and devices are presented in a block diagram form in order to
facilitate the description of the embodiments.
"Component", "module", "system", and the like which are terms used
in the specification refer to a computer-related entity, hardware,
firmware, software, and a combination of the software and the
hardware, or execution of the software. For example, the component
may be a processing process executed on a processor, the processor,
an object, an execution thread, a program, and/or a computer, but
is not limited thereto. For example, both an application executed
in a computing device and the computing device may be the
components. One or more components may reside in the processor
and/or the execution thread, and one component may be localized in
one computer or distributed among two or more computers. Further,
the components may be executed by various computer-readable media
having various data structures, which are stored therein. The
components may perform communication with another system through
local and/or remote processing according to a signal (for example,
data from one component that interacts with other components and/or
data from other systems through a network such as the Internet
through a signal in a local system and a distribution system)
having one or more data packets, for example.
The description of the presented embodiments is provided so that
those skilled in the art of the present disclosure use or implement
the present disclosure. Various modifications of the embodiments
will be apparent to those skilled in the art, and general
principles defined herein can be applied to other embodiments
without departing from the scope of the present disclosure.
Therefore, the present disclosure is not limited to the embodiments
presented herein but should be analyzed within the widest range,
which is consistent with the principles and new features presented
herein.
The terms "current pulse generating device" and "exploration
current generating device" used in the specification may be often
used to be exchanged with each other. The terms "voltage pulse
generating device" and "leak detection voltage signal generating
device" used in the specification may be often used to be exchanged
with each other.
The present disclosure relates to a device and a method for
providing information on a suspicious earth leaking area and a leak
source to limit an exploration area effectively under the
environment where in the middle of a power cable have several PENs
(Protective Earthed Neutral) that ground a neutral line at
different locations such as MEN (Multiple Earthed Neutral)
configuration.
In order to distinguish actual leak voltage from a parasitic
voltage source which continuously exists in proximity to a power
facility charged with a commercial power source, as a result of
measuring the waveforms, an induced voltage of conductors
electrostatically or magnetically coupled to the power lines or a
stray voltage generated by the current flows in the ground out from
a neutral line are illustrated in FIG. 7 or 8. In other words, a
waveform of earth voltage of which potential rises at a true leak
location of the commercial power which flows out to the ground due
to an insulation failure of the power facility has a pure sine
waveform contains a power frequency illustrated in FIG. 6. On the
other hand, a parasitic voltage waveform has multiple components of
different phases and magnitudes are synthesized together.
As illustrated in FIG. 3, the AC commercial power has relatively
high internal impedance at a ground leak point 207, so even though
a voltage drop occurs through R1 until reaching a ground surface,
but the earth voltage at a measurement point has a sine wave
characteristic of a single pure power frequency (50 or 60 Hz)
characteristic not including external noise or the like as
illustrated in FIG. 6.
In view thereof, in the related art, as illustrated in FIG. 2, a
content rate which is a ratio a total voltage value (V1) to a
voltage value (Vf) of the power frequency (50 or 60 Hz), and a
variation rate of voltage are acquired for confirming whether the
earth voltage is raised from the actual voltage, however, a portion
where the earth voltage rises by the parasitic voltage (induced and
stray voltage) may not be distinguished, and as a result, this case
is problematic to determine as the true leak mistakenly.
FIG. 7 illustrates an example of a parasitic voltage waveform.
Although the parasitic waveform is similar to the power frequency
(60 Hz) waveform, the content rate is less than 85%, and the
corresponding voltage is found as the parasitic voltage. As a
result, there is no problem, but in FIG. 8, even though the
parasitic voltage is not a pure waveform, but a distorted, the
content rate is maintained to be 85% or more, and this case may be
mistaken as the true leak.
FIG. 9 exemplifies a method of counting the number of times of
zero-crossing of the earth voltage at a location of a leak point in
order to distinguish FIG. 8, and a magnitude of a power frequency
and a harmonic thereof after Fourier transforms.
FIG. 10 illustrates a method of counting the number of times of
zero-crossings of the earth voltage at a buried location of a
parasitic voltage source and a magnitude of a power frequency and a
harmonic thereof after Fourier transforms in the same manner as
FIG. 9.
As illustrated in FIGS. 9 and 10, by counting the number of times
of zero-crossing in addition to the content rate of the input earth
voltage, even if the parasitic voltage illustrated in FIG. 7 has
the content rate of 85% or more, a zero-crossing count (ZCC) is 10
in the true leak when the number of times of zero-crossing is
counted for 5 cycles in an actual example, but the parasitic
voltage has ZCC which is more than 10 to identify the parasitic
input voltage.
As illustrated in FIGS. 9 and 10, by counting the number of
zero-crossing in addition to the content rate of the input earth
voltage, even if the parasitic voltage illustrated in FIG. 7 has
the content rate of 85% or more, a zero-crossing count (ZCC) is 10
in the true leak when the number of zero-crossing is calculated for
5 cycles in an actual example, but the parasitic voltage has ZCC
which is more than 10 times, the input signal can be distinguished
as parasitic voltage.
FIG. 11 illustrates a distortion count (DC) at a location with a
distorted waveform.
FIG. 12 illustrates a method for counting the number of locations
where distortion occurs as illustrated in FIG. 11. In other words,
the comparison between the current signal value and the previous
signal value is obtained, and if the polarity is reversed, one
count may be added, and FIG. 13 is a flow chart illustrates a DC
count workflow for every 5 cycles period of AC commercial voltage.
For example, when an immediately previous sampling signal value is
higher than a before-last sampling signal value, and a current
sampling signal value and the immediately previous sampling signal
value are compared, and when the polarity is inverted, one count
may be added. Further, when the immediately previous sampling
signal value is smaller than the before-last sampling signal value,
the immediately previous sampling signal value and the before-last
sampling signal value may be compared, and as the comparison
result, when the before-last sampling signal value is greater than
or equal to the immediately previous sampling signal value, the
current sampling signal value and the before-last sampling signal
value are compared, and when the current sampling signal value is
higher than the immediately previous sampling signal value, it
could be determined that the polarity is inverted to be added one
count. That is, the polarity is determined by obtaining differences
of the before-last, immediately previous, and current sampling
signal values to perform the distortion count work for every 5
cycles. The counting workflow is just an example and the present
disclosure is not limited thereto.
As an example, according to the present disclosure, FIG. 28
illustrates a screen 60 in which the ZCC or DC may be selected at
the time of determining the distortion of the waveform, and when
not ZCC 61 but DC 62 is selected, a size (a size of a sample
difference for deciding polarity inversion for counting the DC) of
a different value needs to be set at a screen 63. In the example,
it can be seen that the size of the sample difference is set to
2069.
It can be seen that DC count value 48 in FIGS. 23 and 27 is 17 at
the true leak location, but 49 at the parasitic voltage location
and when the counter number of the DC is ranged 8<DC<28, the
corresponding voltage is determined as the true leak voltage and
when the DC is out of the range, the corresponding voltage is
determined as the parasitic voltage to be disregarded.
As a result of the Fourier transform as illustrated in FIG. 9, the
fundamental frequency component of 60 Hz, which is the power
frequency, occupies the majority at the true leak point, which is
in agreement with the content ratio of 85% or more of the
conventional method, but as illustrated in FIG. 10, it can be
observed that the fundamental frequency components of 60 Hz
decrease in the parasitic voltage, while other harmonic components,
including 180 Hz, which is a third harmonic increase.
Consequently, the input earth voltage signal will be Fourier
transformed by software rather than hardware filtering to improve
the accuracy of the conventional content rate, the threshold values
of the THD by harmonics of the fundamental frequency of power
systems, and other harmonic frequencies are designated to operate
as follows.
The following is a measurement table of voltage values of the power
frequency and each odd harmonic spectrum voltage value when the
true leak voltage and the parasitic voltage of FIGS. 21 and 25 are
Fourier-transformed.
TABLE-US-00001 TABLE 1 Frequency spectrum Voltage value (V)
Fundamental frequency (V1) 2.892 Third harmonic (V3) 0.114 Fifth
harmonic (V5) 0.034 Seventh harmonic (V7) 0.017 Ninth harmonic (V9)
0.016 Total (Vt) 3.073
TABLE-US-00002 TABLE 2 Frequency spectrum Voltage value (V)
Fundamental frequency (V1) 1.751 Third harmonic (V3) 0.248 Fifth
harmonic (V5) 0.062 Seventh harmonic (V7) 0.039 Ninth harmonic (V9)
0.035 Total (Vt) 2.135
Table 3 shows a result of obtaining a harmonic distortion rate as
follows based on the measurement values of Tables 1 and 2
above.
.times..times..times..times..times..times. ##EQU00001##
TABLE-US-00003 TABLE 3 True leak Parasitic Threshold Classification
voltage voltage value Note Content rate (V1/Vt) 94.11% 82.01%
85.5%> THD 4.20% 14.90% <10% THD_F3 3.94% 14.16% <10%
THD_F5 1.17% 3.54% <3% THD_F7 0.58% 2.22% <2%
As shown in Table 3, by setting the content rate and the threshold
value for each harmonic, only the earth voltage signal within the
threshold value is defined as the true leak voltage to allow this
region to be determined as the suspicious earth leaking area where
the leak source may exist. The present disclosure is not limited to
the method and the device for detecting the leak source location
like the example of the present disclosure by measuring the content
rate and the THD, the ZCC, or the DC of the power frequency signal
(fundamental frequency) included in the signal as described above,
but will be able to be used even as a technique that finds an
insulation failure location of the power facility even in other
diagnostic techniques.
FIG. 14 is a diagram illustrating an electrical leak suspecting
section exploration configuration of an electrical leak detecting
device 1000 capable of freely moving on an arbitrary site and
determining a suspected electrical leak section without
transmitting (injecting) a leak exploration signal according to the
present invention. Unlike before, the Fourier transform is used
without using a hardware filter to obtain the voltage (V1) of the
fundamental frequency (60 Hz) and the total voltage (Vt) to obtain
the content rate, THD, and etc, and ZCC or DC is counted in order
to determine the distortion of the waveform.
FIG. 15 illustrates a flowchart of suspicious earth leaking area
exploration work, which is a function of FIG. 14.
As illustrated in FIG. 15, in order to determine the suspicious
earth leaking area, first, the earth voltage V1 between the neutral
line and remote earth is measured so as to determine whether the
earth voltage V1 exceeds a threshold value (500 mV) and has a
content rate value including a power frequency component Vf of a
predetermined ratio (0.855) or more. Further, the zero-crossing
count (10 times) of the earth voltage V1 is confirmed at the leak
point location, and the distortion count (DC) is made to determine
not the pure sine wave accurately, but the waveform including the
distortion and when 8<DC<28, the corresponding voltage may be
determined as the true leak voltage and when the DC deviates from
the scope, the corresponding voltage may be determined as the
parasitic voltage. In addition, as shown in <Table 3> above,
only the earth voltage signal within the threshold value range for
each harmonic may be determined as the true leak voltage. That is,
it may be that there is the suspicious earth leaking area where the
leak source may exist according to whether to satisfy the
determinations and the suspicious earth leaking area exploration
work may be terminated.
FIG. 16 is a diagram illustrating a configuration of exploring an
earth leakage point of an electrical leak detecting device 1000
capable of moving along a power facility (power line) within the
suspected area by transmitting (injecting) a leak exploration
signal into the facility according to the present disclosure. When
the leak point exploration is performed, as illustrated in FIG. 3,
the leak exploration voltage and current signals are injected into
power lines 202 and 203 in the suspicious earth leaking area, and
the magnetic field pulse signals 111 and 112 generated by the leak
exploration current signal flowing in the power line are obtained
on the ground surface. The leak detecting device 1000 moves along a
buried path of the power lines 202 and 203 and performs the leak
exploration to find the leak point location by contacting the earth
surface 105 and 106 and measuring the earth voltage. Specifically,
leak exploration signal generating devices 302 and 303 are
connected to the power lines 202 and 203 in the suspicious earth
leaking area and the magnetic field pulse signals 111 and 112
generated by the current signal transmitted by the current pulse
signal device 302 are detected on the earth. The earth voltage 212
is measured by contacting the leak detecting device 1000 with the
ground surface 105 and 106 while moving along the buried path on
the ground surface. At this time, the magnetic field signals 111
and 112 used in the path exploration are received and assessed in
accordance with a generation time of the next leak exploration
voltage pulse signal 110 to be generated and a coding value,
including the leak exploration voltage pulse signal 110 is analyzed
to determine the authenticity and if the coding value matches, a
maximum signal detected location of the leak exploration voltage
pulse signal 110 may be determined as the earth leakage point.
FIG. 17 illustrates a flowchart of the leak exploration work using
the configuration of FIG. 16.
As illustrated in FIG. 17, when the magnetic field signal by the
current signal is detected, the measurement start time is provided
to distinguish an earth voltage (Vrms), a content rate, a ZCC/DC,
and a THD to identify the rise of the earth potential by the true
earth leakage. Further, when the corresponding leak is determined
as the true leak, the exploration signal generating device (current
and voltage) is connected to the power line to determine a reach
time of the exploration voltage signal after receiving the magnetic
field signal and determine a maximum value location of the leak
exploration voltage signal by considering whether to match the
coding value of the leak exploration voltage signal.
Compared with the related art, the input earth voltage was filtered
with hardware to calculate the content rate by using a ratio of a
magnitude of the power frequency component and the total voltage.
The present disclosure presents the way to increase the accuracy of
the content rate to distinguish the actual leak from the earth
voltage rise because of the parasitic source by calculating a ratio
of a sum (total harmonics) of harmonic components and a component
of power frequency after Fourier transform, thereby enhancing
accuracy by adding a function to determine a distortion degree of
the waveform.
Besides, the previous technology omits a parasitic voltage
filtering function under the assumption that there is only a true
leakage when exploring a leak point within a suspected leak area,
and the magnitude of the earth voltage was measured to determine an
earth leakage point without consideration of other sources of earth
voltage rising. But the application of prior art in the field, it
was found that parasitic voltages could exist even within the earth
leaking suspicious area. In the earth leakage point detection,
unlike before, a leakage point alarm is generated according to the
earth leakage detection result only after determining whether the
true earth voltage of the input earth voltage is true.
FIG. 18 illustrates a result of the exploration of a suspicious
earth leaking area for each location according to the present
disclosure. It can be seen that since the earth voltage (Vrms), the
content rate, the ZCC/DC, and the THD do not reach the threshold
values at a portion other than the leak point, the alarm is
accurately generated only at the leak point location.
FIG. 19 shows the results of the earth leakage point exploration by
location. An earth leakage location is alarmed by the leak
detecting device by sound and a screen of the leak detecting device
shows a blinking red color lamp and signal level to locate the
maximum signal position so that it can be judged as the earth
leakage point. If the earth potential rises above 500 mV at the
location of a parasitic voltage source as shown on the right side
of the FIG. 19, the filtering algorithms based on DC (distortion
counter) and THD of third harmonic block the alarm, therefore, even
if the earth voltage rise is detected, but it could be determined
to be not true leakage and be ignored.
Next, a screen configuration of the leak detecting device 1000
according to the present disclosure will be described.
FIGS. 20 to 23 are screens showing a result of measurement at a
true leak voltage location. FIG. 20 illustrates a suspicious earth
leaking area exploration screen 29, and V1 21 represents the sum of
all harmonic voltages, Vf 22 represents a fundamental frequency
voltage of 60 Hz which is the power frequency, and R 23 represents
the content rate. Further, Z 24 represents the ZCC and reference
numerals 25, 26, 27, and 28 show whether THD and odd harmonic THD
do not exceed the threshold values by colors. That is, as reference
numerals 25, 26, 27, and 28, all four of the earth voltage (Vrms),
the content rate, the ZCC/DC, and the THD satisfy conditions of the
threshold values to be expressed by all red-colored boxes. When all
of the conditions are satisfied, a user determines that the true
leak source exists around the corresponding location to display a
leak alarm 33 and perform the leak point exploration work, which
might be the next process.
FIG. 21 shows a potential value for each spectrum as a result of
the Fourier transform shown when button FFT_V 31 of FIG. 20 is
pressed. It can be seen that the voltage of a fundamental frequency
5 is 2.8926 V (2), and the total voltage is 3.08 V (1). When the
voltage of the fundamental frequency 5 and the total voltage are
calculated, a content rate 4 is 94%, and even though all is not
shown, the device determines that all conditions are satisfied to
generate a leak alarm 3.
FIG. 22 is an exemplary diagram illustrating a waveform screen
shown when a waveform (32) button of FIG. 20 is pressed. A form of
the waveform of the measured earth voltage may be observed, and
information on V1 11 which is the sum of all harmonic voltages, Vf
12 which is the fundamental frequency voltage of 60 Hz, which is
the power frequency, the content rate 13, the ZCC 15, and the leak
alarm 14 may be confirmed.
FIG. 23 is an exemplary diagram illustrating a screen captured at a
maximum point of the leak signal after connecting an exploration
signal device to a power line as a place illustrated in FIG. 20 is
determined as a suspicious earth leaking area. A leak signal value
indicates 4,625 (41), and the resulting coding values 56 and 57 are
displayed. Other matters are used for determining the true leak
voltage or not and are the same as in FIG. 20.
FIGS. 24 to 27 illustrate an example of a screen showing a result
of measuring the parasitic voltage. FIG. 24 illustrates a screen 29
of exploring the suspicious earth leaking area or not by measuring
the earth voltage of which potential rises by the parasitic
voltage, and the remaining description is the same as FIG. 20.
However, the total earth voltage V1 21 does not reach the threshold
value of 500 mV, and the content rate R 23 does not also reach 85%.
It can be seen that the distortion count shows 49, and most THDs do
not satisfy the threshold value.
FIG. 25 shows the result of the Fourier transform of the earth
voltage in FIG. 24. It can be seen that the content rate 4 is 82%,
and the values of the fundamental frequency spectrum voltages 5 and
2 are relatively low, and the value of the third harmonic voltage 6
is higher than others and since all conditions are not satisfied,
the leak alarm 3 is not generated.
FIG. 26 illustrates an earth voltage waveform that appears when the
waveform 32 of FIG. 24 is selected and input. As illustrated in
FIG. 26, it can be seen that the corresponding waveform is the
waveform containing a lot of distortion other than the pure sine
wave. When it is considered that the distortion count 15 at the
lower corner shows 47 times during 5 cycles, it may be easily
determined that the corresponding voltage is the parasitic voltage
having severe distortion other than the pure sine wave only by the
DC count 15 without viewing the waveform. It is also possible to
confirm that the leak alarm 14 is not generated, and the total
earth voltage V1 11, the fundamental frequency voltage Vf 12, and
the content rate 13 may be the same as shown in the drawing of FIG.
24.
FIG. 27 is an exemplary diagram illustrating a screen captured at a
maximum point of the leak signal at the place illustrated in FIG.
24 after connecting an exploration signal device to a power line in
order to reconfirm whether the erroneous determination occurs as
related art even though the place is not determined as the
suspicious earth leaking area before. The leak signal value
indicates 4,625 (41) by the parasitic voltage, but the coding
values do not coincide with each other, the leak signal value is
not displayed, and it can be seen that the corresponding voltage is
not the true leak voltage by considering that the DC count is 49
(48) and the content rate is 80% (49), and even though the leak
voltage signal included in the parasitic voltage is detected, the
corresponding voltage may not pass through other true leak voltage
determination logic, and as a result, the leak signal is ignored,
and the leak alarm is not generated so as not to be determined as
the leak point.
FIG. 28 is a screen for selecting ZCC or DC to be counted in order
to judge distortion or the like of the earth voltage waveform.
As described above, the present disclosure is a technology for
finding a position where a part of power flows to the ground
unintentionally and increases the ground voltage due to an
insulation failure of a power facility that transmits or stores the
AC commercial power. Unlike the previous technology, the present
disclosure compares the configuration of voltages for each harmonic
by Fourier analysis of the voltage measured on the ground, compares
the distortion degree of the waveform. It has the advantage that
the accident is precisely explored in advance to prevent any hurt
by innocent pedestrians by performing maintenance work in proper
time.
FIG. 29 is a block diagram of a leak detecting device according to
another embodiment of the present disclosure.
Referring to FIG. 29, when the earth leakage detecting device 1000
satisfies a preset condition by measuring a ground voltage, the
ground fault detecting device 1000 may determine that an earth
leakage out of the power line causes the measured ground voltage.
In detail, in a Multiple Ground Neutral (MEN) environment, having a
plurality of power line PENs (Protective Earthed Neutral) that
ground the neutral line, the leak detecting device 1000 may measure
the earth voltage at any power line PEN. When the measured earth
voltage satisfies the predetermined condition, the leak detecting
device 1000 may determine the suspicious earth leaking area that
the leak occurs in the power line buried around the power line PEN
measuring the earth voltage. When the suspicious earth leaking area
is determined, the leak detecting device 1000 may receive a
magnetic field signal generated from the exploration current
generator to measure the earth voltage along a route in which the
power line installed in the suspicious earth leaking area. The
earth voltage measured on the buried path includes a leak detection
voltage signal generated from the leak detection voltage signal
generating device, and the leak detecting device 1000 may determine
the leak point where the leak occurs in the power line based on the
leak detection voltage signal. The leak detecting device 1000 may
include an earth voltage measuring unit 1110, an ADC unit 1120, an
effective value calculating unit 1130, a Fourier transforming unit
1140, a content rate calculating unit 1150, a harmonic distortion
rate calculating unit 1160, a zero-crossing estimating unit 1170, a
distortion estimating unit 1180, a suspicious earth leaking area
determining unit 1190, a magnetic field signal receiving unit 1210,
a leak detection voltage signal receiving unit 1220, a power line
buried path search unit 1230, a leak point determining unit 1240
and a display unit 1300.
The earth voltage measuring unit 1110 of the leak detecting device
1000 will be described in detail with reference to FIG. 30.
FIG. 30 illustrates an example for describing a method for
measuring earth voltage in another embodiment of the present
disclosure.
Referring to FIG. 30, the earth voltage measuring unit 1110 may
measure the earth voltage. Specifically, the earth voltage
measuring unit 1110 may include an electrode connected to a
measurement point "a", which is a predetermined point on the ground
surface, another electrode connected to a measurement point "b",
which is a predetermined point on the ground surface different from
the measurement point "a", a resistance array connected in parallel
between the measurement points "a" and "b", and a voltage measuring
unit measuring voltage between both ends of the resistance
array.
More specifically, when an electrical earth leakage of the power
line occurs under the ground, the leaked current is designed to be
returned to the power line PEN at the shortest distance. The earth
voltage measuring unit 1110 may measure the earth voltage
proportional to the earth resistance Rg and the leak current of AC
commercial power (in Korea, AC 60 Hz, 220V) caused by the
insulation failure of the phase wire for power supply business.
For example, as shown in FIG. 30, when the AC commercial voltage is
leaking out under the ground, each location of "a" and "b" in the
soil might have its value of the distributed earth potential "a"
and "b" according to the distance of earth resistances (Rg) to the
earth leaking source of AC commercial voltage and the PEN. The
earth potential of "a" and "b" in the soil could not be directly
measured, but the earth leak detection device 1000 measures the
earth potential on the ground surface by contacting the measurement
point "a" and "b" instead to locate the earth leaking point which
is underground.
The earth potentials "a" and "b" for each position in the ground
are influenced by the resistance Rp including the earth resistance,
the pavement layer resistance, and the contact resistance from the
points "a" and "b" in the soil to reach the surface.
As shown in the graph of the earth potential distribution on the
ground of the AC commercial power at the top of the Figure, the
potential values of the earth potentials "a" and "b" for each
position underground are changed while reaches the measurement
points "a" and "b" by passing through two Rp (2.times.Rp).
As mentioned above, the potential value changes on the ground
surface due to the effect of the resistance value Rp, and the
problem is that the amplitude of the input potential is not large
enough to be discerned due to the short distance between the
electrodes. To solve this problem, the electrode at measurement
point "a" is connected to a metal body (such as a manhole cover)
that is equipotential to the power line PEN by bonding. Because in
a structure housing such as a utility hole (ex, manhole) having a
power line PEN, a metal cover is bonded to a grounded neutral line
and maintains an equal potential (equipotential) without a
potential difference between charged conductive bodies, and the
earth voltage measuring unit 1110 measures the earth voltage by
using the neutral line voltage as a measurement reference
voltage.
When the voltage of power line PEN which is an equipotential bonded
to the neutral line in the power cable is used as the reference
voltage to measure the earth voltage, the influence of the
resistance Rp at the measurement point "a" may be reduced and the
earth voltage having a stable and large amplitude of potential
difference might be measured. In addition, unlike the related art,
there is no need to access the inside of the structure where the
power line PEN is installed, so that a working environment may be
improved and work time may be saved. The method for measuring the
earth voltage is just an example, and the present disclosure is not
limited thereto.
Referring again back to FIG. 29, the ADC unit 1120 of the leak
detecting device 1000 samples the measured earth voltage and
converts the sampled earth voltage into a digital value.
Specifically, the earth voltage measured by the earth voltage
measuring unit 1110 has an analog value, and the ADC unit 1120
samples the measured earth voltage value, converts the sampled
earth voltage value into a digital value and outputs the digital
value.
The effective value calculating unit 1130 of the leak detecting
device 1000 calculates an effective value of the earth voltage
converted into the digital value.
The earth voltage generated by the leak of the AC commercial power
has a more significant value than the ground voltage generated by
the induced voltage or stray voltage, which is parasitic around the
power line. Therefore, when the effective value of the earth
voltage calculated by the effective value calculating unit 1130 has
a more significant value than the predetermined threshold voltage
value (e.g., 500 mV), it may be determined that the measured earth
voltage is generated by the leak of the AC commercial power.
The Fourier transforming unit 1140 of the leak detecting device
1000 performs a Fourier transform on the measured earth voltage to
calculate voltage for each harmonic component which is an integer
multiple of the fundamental frequency--the power frequency of the
AC commercial power--based on the effective value of the earth
voltage.
Even if the earth voltage measured by the leak detecting device
1000 is generated by the leak of the power line, the earth voltage
may include the harmonic components due to disturbance such as the
parasitic voltage, the earth resistance, and the like. Therefore,
it is difficult to determine whether the earth voltage measured is
caused by the leak of the AC commercial power when combined with
the harmonic components. So that it is necessary to analyze how
many harmonic components the earth voltage contains. The Fourier
transforming unit 1140 performs the Fourier transform of the
measured earth voltage to calculate a voltage value having the
fundamental frequency and the voltage value for each harmonic
component which is an integer multiple of the fundamental frequency
by setting 60 Hz, which is the power frequency of the AC commercial
power (in the case of Korea, AC 60 Hz 220 V) as the fundamental
frequency.
As described above, referring back to FIGS. 9 and 10, the Fourier
transforming unit 1140 of the measured earth voltage may calculate
the voltage value for each harmonic component, which is an integer
multiple of the fundamental frequency. The measured earth voltage
in FIG. 9 shows a voltage of a fundamental frequency (60 Hz) is
higher than that of an integer multiple of the fundamental
frequency, such as 120 Hz, 180 Hz, and 240 Hz, which are harmonic
components, and thus it can see that the harmonic effect due to
disturbance was less influential. Therefore, it may be determined
that the measured earth voltage is generated by the leak of the AC
commercial power. On the contrary, the measured earth voltage
illustrated in FIG. 10 shows the harmonic components of the integer
multiple of the fundamental frequency have higher amplitude than
that of 60 Hz, and so it can ascertain that the harmonics much
influenced the earth voltage value due to the disturbance.
Therefore, it may not be determined that the measured earth voltage
is generated by the leak of the AC commercial power.
Based on the voltage value of the base frequency and that of
harmonics of the base frequency transformed by the Fourier
transforming unit 1140, the content rate calculating unit 1150 may
calculate the voltage content rate that is the ratio of a voltage
value of the fundamental frequency to the voltage values obtained
by adding the voltage for each harmonic component. In addition, the
harmonic distortion rate calculating unit 1160 can calculate the
total harmonic distortion rate and a harmonic distortion factor
based on the voltage value for fundamental and each harmonic
component.
Based on the voltage of each harmonic component, the content rate
calculating unit 1150 of the leak detecting device 1000 may
calculate the voltage content rate (V1/Vt) by comparing the voltage
of the fundamental frequency to the voltage acquired by adding the
voltages for each harmonic component.
The higher the content rate calculated by the content rate
calculating unit 1150 is, the measured earth voltage has more
components for the fundamental frequency. Therefore, when the
content rate exceeds the predetermined content rate (e.g., 85%), it
may be determined that the measured earth voltage is generated by
the leak of the AC commercial power.
As described above, referring back to Tables 1 and 2, in Table 1,
the content rate of the voltage having the fundamental frequency
component with respect to the total voltage exceeds the
predetermined content rate (for example, 85%), but the content rate
of the voltage having the fundamental frequency component to the
total voltage does not exceed the predetermined content rate (for
example, 85%) in Table 2. Therefore, it may be determined that the
earth voltage measured in Table 1 is generated by the leak of the
AC commercial power. The method for determining that the earth
voltage is generated by the leak based on the content rate is just
an example, and the present disclosure is not limited thereto.
In addition, the harmonic distortion rate calculating unit 1160 of
the leak detecting device 1000 may calculate the total harmonic
distortion rate and a harmonic distortion factor based on the
voltage for each harmonic component.
The total harmonic distortion rate may be calculated by Equation 3.
The harmonic distortion factor may be calculated by Equation 4. It
shows that the higher the total harmonic distortion rate and the
harmonic distortion factor by the harmonic element, the more
harmonic components are included.
When the total harmonic distortion calculated by the harmonic
distortion rate calculating unit 1160 is less than a predetermined
distortion rate and when the harmonic distortion factor is less
than a predetermined distortion rate, it may be determined that the
measured earth voltage is less influenced by the harmonics. When it
is determined that the measured earth voltage is less influenced by
the harmonics, accuracy and reliability may be increased, which may
determine that the earth voltage is generated by the leak of the AC
commercial power by calculating the effective value, the content
rate, and the zero-crossing count based on the measured earth
voltage.
The zero-crossing estimating unit 1170 of the leak detecting device
1000 may estimate the zero-crossing count at which the earth
voltage converted into the digital value passes through zero
voltage for a predetermined time T1. Here, the predetermined time
T1 may be a time which is a predetermined integer multiple of a
cycle of the AC commercial power.
The zero-crossing estimating unit 1170 may estimate the
zero-crossing count passing through the zero voltage when the
polarity of the earth voltage is changed for the predetermined time
T1.
The number of zero-crossings in a measured earth voltage estimated
by the zero-crossing estimating unit 1170 may contain most of the
fundamental frequency in AC commercial power, and it could
determine that the leakage of AC commercial voltage generates the
earth voltage at the measuring place.
For example, the predetermined time T1 may be set to 5 times of the
cycle of the AC commercial power. In this case, the zero-crossing
count of AC commercial power is 10. If the zero-crossing count of
the measured earth voltage is 10, it may be determined that the
earth voltage contains more 60 Hz components and the measured earth
voltage is generated by the leak of the AC commercial voltage. On
the other hand, if the zero-crossing count of the measured earth
voltage exceeds 10, it may be determined that the earth voltage
contains more frequency components other than 60 Hz and the earth
voltage is generated by the influence of the harmonics or by the
parasitic voltage.
Further, as described above, referring back to FIG. 7, the measured
earth voltage is similar to the 60 Hz waveform, which is the power
frequency. However, since the content rate is less than the
predetermined content rate (for example, 85%), it may be determined
that the earth voltage is not generated by the leak but the
parasitic voltage. Referring back to FIG. 8, the content rate of
the measured earth voltage exceeds the predetermined content rate
(e.g., 85%), but the waveform is not similar to the waveform of 60
Hz, which is the power frequency and the zero-crossing count of the
earth voltage exceeds the zero-crossing count of the AC commercial
power for the predetermined time T1. So, it may be determined that
the earth voltage is not generated by the leak, but raised by the
influence of the harmonics or the parasitic voltage.
The method for determining that the earth voltage is generated by
the leak of the AC commercial voltage based on the zero-crossing
count is just an example, and the present disclosure is not limited
thereto.
The distortion estimating unit 1180 of the leak detecting device
1000 may estimate the distortion count, which is the number of
times at which the distortion by the harmonics occurs in the
measured earth voltage for the predetermined time T1. Here, the
predetermined time T1 may be a time which is a predetermined
integer multiple of a cycle of the AC commercial power.
A specific method of estimating the number of distortions by the
distortion estimating unit 1180 will be described with reference to
FIGS. 31 and 32.
FIG. 31 illustrates an example for describing a method for
calculating the number of distortions, according to another
embodiment of the present disclosure.
Referring to FIG. 31, when the polarity of a first change amount of
a digital value of first earth voltage converted through sampling
and a digital value of second earth voltage converted through
sampling after a next sampling period and the polarity of a second
change amount of a digital value of the second earth voltage and a
digital value of third earth voltage converted through sampling
after a next sampling period are different from each other, the
distortion estimating unit 1180 determines that the distortion by
the harmonics occurs to estimate the distortion count. For example,
when the digital value of the first earth voltage is 50 mV and the
digital value of the second earth voltage sampled next is 53 mV,
the first change amount as (+)3 mV has a positive polarity. When
the digital value of the third earth voltage sampled next is 52 mV,
the second change amount as (-) 1 mV has a negative polarity. In
this case, the polarity of the first change amount and the polarity
of the second change amount are different from each other, and it
may be determined that the distortion by the harmonics occurs and
the distortion count may be estimated.
FIG. 32 is a flowchart for the method for calculating the number of
distortion times according to another embodiment of the present
disclosure.
Referring to FIG. 32, when the polarity of the first change amount
is different from the polarity of the second change amount, the
distortion estimating unit 1180 may estimate one time as the
distortion count. When the total distortion count estimated for the
predetermined time T1 is less than a predetermined distortion
count, it is determined that the harmonics fewer influences the
measured earth voltage. When it is determined that the harmonics
less influences the measured earth voltage, accuracy and
reliability may be increased, which may determine that the earth
voltage is generated by the leak of the AC commercial power by
calculating the effective value, the content rate, and the
zero-crossing count based on the measured earth voltage.
Referring back to FIG. 29, the suspicious earth leaking area
determining unit 1190 of the leak detecting device 1000 may
determine that the earth voltage is generated by the leak of the AC
commercial power based on at least any one of the effective value
of the earth voltage, the voltage content rate, the total harmonic
distortion, the harmonic distortion factor, the zero-crossing
count, and the distortion count and determine a region where the
earth voltage is measured as the suspicious earth leaking area
based on the determination result.
More specifically, the suspicious earth leaking area determining
unit 1190 may determine that the earth voltage is generated by the
leak of the AC commercial power when the effective value of the
earth voltage exceeds a predetermined threshold voltage value, the
voltage content rate exceeds a predetermined voltage content rate,
the total harmonic distortion is less than a predetermined total
harmonic distortion, the harmonic distortion factor is less than a
predetermined harmonic distortion factor, the zero-crossing count
coincides with a predetermined count, and the distortion count is
less than a predetermined count. The method for determining the
suspicious earth leaking area is just an example, and the present
disclosure is not limited thereto.
When the suspicious earth leaking area determining unit 1190
determines an area as a suspicious earth leaking area where might
have an earth leak source of AC commercial power around after
measuring an earth voltage reference to a power line PEN, then the
leak point determining unit 1240 may determine an earth leaking
point by an actual earth leaking source along a buried cable path
of the said power line PEN.
The magnetic field signal receiving unit 1210 of the leak detecting
device 1000 may receive the magnetic field signal generated from
the exploration current generating device.
As described above, the exploration current generating device
injects the current signal into the phase and neutral line within
the suspicious earth leaking area, and the magnetic field signal
receiving unit 1210 may receive the magnetic field signal generated
by flowing current of exploration signal which flows through the
phase and neutral line in the ground.
The magnetic field signal receiving unit 1210 may include a
plurality of magnetic field sensors and may receive the magnetic
field signal polarity and the magnitude of the magnetic field
signal.
The power line buried path search unit 1230 of the leak detecting
device 1000 may search the path of the power line buried in the
suspicious earth leaking area based on the received magnetic field
signal.
For example, the power line buried path search unit 1230 may
determine a point where the magnitude of the magnetic field signal
is the maximum point as a buried power line path. Further, the
power line buried path search unit 1230 may search a direction of a
path in which the power line is buried based on the magnetic field
signal polarity.
The leak detection voltage signal receiving unit 1220 of the leak
detecting device 1000 may receive the leak detection voltage signal
generated from the leak detection voltage signal generating
device.
As described above, the leak detection voltage signal generating
device transmits the leak detection voltage signal, which is DC
pulse voltage, to the power line. When the leak occurs in the power
line, the AC commercial power and the leak detection voltage signal
to be measured together in the earth voltage, but the earth voltage
also includes harmonic components so that it might be difficult to
identify the leak detection voltage signal out of the earth voltage
when mixed with other components measured by the earth voltage
measuring unit 1110. Therefore, the leak detection voltage signal
generating device transmits the leak detection voltage signal after
a predetermined set time from when the time of the exploration
current generating device transmits the exploration current signal.
Based on the time, when the magnetic field signal receiving unit
1210 receives the magnetic field signal generated by the
exploration current transmitter, the leak detection voltage signal
receiving unit 1220 may detect the leak detection voltage signal in
the earth voltage measured on the ground surface after a certain
time of receiving the magnetic field signal.
The leak point determining unit 1240 of the leak detecting device
1000 may determine the leak point of the power line buried based on
the leak detection voltage signal.
The leak point determining unit 1240 may set a logical value
according to whether receive the leak detection voltage signal and
determine a point where the set logical value and a logical value
of the leak detection voltage signal generated by the leak
detection voltage signal generating device coincide with each other
and the magnitude of the leak detection voltage signal has a
maximum value as the leak point.
A detailed description of the leak point determining unit 1240
moving along the power line buried path and determining the leak
point of the power line will be described below with reference to
FIGS. 33 and 34.
FIG. 33 is an explanatory diagram of a protocol for receiving a
magnetic field signal and receiving a leak detection voltage signal
according to another embodiment of the present disclosure.
As a specific example with reference to FIG. 33, when the magnetic
field signal receiving unit 1210 receives a magnetic field signal
`0101000` having a discontinuous characteristic generated from the
exploration current generating device, the power line buried path
search unit 1230 sets a magnetic field signal start time. The power
line buried path search unit 1230 measures the magnetic field
signal value every power frequency cycle after the magnetic field
signal start time to search the power line buried path based on the
polarity and the magnitude of the magnetic field signal.
The leak detecting device 1000 measures the earth voltage on the
ground surface above a buried path of the power line and moves
along the path. The leak detection voltage signal receiving unit
1220 receives the leak detection voltage signal at the earth
voltage measured on the path where the power line is buried. The
leak point determining unit 1240 analyzes the logical value
included in the leak detection voltage signal and compares the
magnitude of the leak detection voltage signal when the logical
value is `1` to determine the point where the leak detection
voltage signal has the maximum value as the leak point.
FIG. 34 illustrates an example showing a relationship between a
leak detection voltage signal start time notification and a time
when the leak detection voltage signal is measured according to
another embodiment of the present disclosure.
Referring to FIG. 34, each of 3-phase powers has a phase difference
of 120 degrees, and a sine wave voltage waveform is repeated. When
the exploration current generating device transmits the exploration
current signal to a C-phase power line, the leak detection voltage
signal generating device transmits the leak detection voltage
signal to an A-phase power line in which a phase is lagged by 120
degrees. The leak detection voltage signal is transmitted after a
predetermined time (e.g., a time within 1/3 cycle after the time of
transmitting the exploration current signal) from the time of
transmitting the exploration current signal. When the exploration
current signal generates the magnetic field signal and the magnetic
field signal receiving unit 1210 receives the magnetic field
signal, the leak detection voltage signal receiving unit 1220
receives the leak detection voltage signal after the predetermined
time (e.g., the time within 1/3 cycle after the time of
transmitting the exploration current signal) from the time of
transmitting the exploration current signal) from the time when the
magnetic field signal receiving unit 1210 receives the magnetic
field signal.
The display unit 1300 of the leak detecting device 1000 may display
whether the measured earth voltage is caused by the leak of the AC
commercial power.
Referring back to FIGS. 20 to 28, as described above, the display
unit 1300 may display a voltage magnitude of the power frequency
and a voltage magnitude obtained by adding the voltage for each
harmonic component. Further, the display unit 1300 may display the
content rate of the measured earth voltage, the zero-crossing
count, and the distortion count. In addition, the display unit 1300
may display the magnitude of the voltage of each harmonic component
and display whether the harmonic distortion factor is less than the
predetermined distortion rate through color classification.
Further, the display unit 1300 may display the logical value of the
leak detection voltage signal and can display the power line of the
leaked phase.
FIG. 35 is a flowchart for a method for determining another
suspicious earth leaking area according to another embodiment of
the present disclosure.
The leak detecting device 1000 may measure the earth voltage
(S1101). Specifically, in the case where the leak occurs in the
power line in the ground, the leak current is designed to be return
to the power line PEN within the shortest distance. The leak
detecting device 1000 may measure the earth voltage based on the
earth resistance Rg and the leak current of AC commercial power (in
Korea, AC 60 Hz, 220V) caused by the insulation failure of the
power line (commercial line) for power supply.
The leak detecting device 1000 samples the measured earth voltage
and converts the sampled earth voltage into the digital value
(S1102).
Specifically, the earth voltage measured by the leak detecting
device 1000 has an analog value, and the leak detecting device 1000
samples the measured earth voltage value, converts the sampled
earth voltage value into the digital value and outputs the digital
value.
The leak detecting device 1000 calculates the effective value of
the earth voltage converted into the digital value (S1103).
The earth voltage generated by the leak of the AC commercial power
has a more significant value than the ground voltage generated by
the induced voltage or stray voltage, which is parasitic around the
power line. Therefore, when the effective value of the earth
voltage calculated by the leak detecting device 1000 has a more
significant value than the predetermined threshold voltage value
(e.g., 500 mV), it may be determined that the measured earth
voltage is generated by the leak of the AC commercial power.
The earth leak detecting device 1000 performs a Fourier transform
on the measured earth voltage to calculate voltage for each
harmonic component, which is an integer multiple of the fundamental
frequency--the power frequency of the AC commercial power--based on
the effective value of the earth voltage (S1104).
Even if the leak of the power line generates the earth voltage
measured by the leak detecting device 1000 the earth voltage may
include the harmonic component due to disturbance such as the
parasitic voltage, the earth resistance, and the like. Therefore,
it is difficult to determine whether the earth voltage measured by
the harmonic component is caused by the leak of the AC commercial
power, so that it is necessary to analyze how many harmonic
components the earth voltage contains.
The leak detecting device 1000 performs the Fourier transform of
the measured earth voltage to calculate a voltage value having the
fundamental frequency and the voltage value for each harmonic
component which is an integer multiple of the fundamental frequency
by setting 60 Hz which is the power frequency of the AC commercial
power (in the case of Korea, AC 60 Hz 220 V) as the fundamental
frequency.
As described above, referring back to FIGS. 9 and 10, the Fourier
transforming unit of the measured earth voltage may calculate the
voltage value for each harmonic component, which is an integer
multiple of the fundamental frequency. In can be seen that the
measured earth voltage illustrated in FIG. 9 contains the voltage
having the fundamental frequency of 60 Hz more than the voltage
having the integer multiple of the fundamental frequency, such as
120 Hz, 180 Hz, 240 Hz, or the like which are the harmonic
components, so that the earth voltage may be less influenced by the
harmonics due to the disturbance, and the like. Therefore, it may
be determined that the measured earth voltage is generated by the
leak of the AC commercial power. On the contrary, it can be seen
that the measured earth voltage illustrated in FIG. 10 contains
more voltage having the integer multiple of the fundamental
frequency, such as 120 Hz, 180 Hz, 240 Hz, or the like, which are
the harmonic components, so that the harmonics may much influence
the earth voltage due to the disturbance, and the like. Therefore,
it may not be determined that the measured earth voltage is
generated by the leak of the AC commercial power.
Based on the voltage of each harmonic component, the leak detecting
device 1000 may calculate the voltage content rate (V1/Vt) by
comparing the voltage of the fundamental frequency to the voltage
acquired by adding the voltages for each harmonic component
(S1105).
The higher the content rate calculated by the leak detecting device
1000 is, the measured earth voltage has more components for the
fundamental frequency. Therefore, when the content rate exceeds the
predetermined rate (e.g., 85%), it may be determined that the
measured earth voltage is generated by the leak of the AC
commercial power.
As described above, referring back to Tables 1 and 2, in Table 1,
the content rate of the voltage having the fundamental frequency
component with respect to the total voltage exceeds the
predetermined content rate (for example, 85%), but in Table 2, the
content rate of the voltage having the fundamental frequency
component to the total voltage does not exceed the predetermined
content (for example, 85%). Therefore, it may be determined that
the earth voltage measured in Table 1 is generated by the leak of
the AC commercial power. The method for determining that the earth
voltage is generated by the leak based on the content rate is just
an example, and the present disclosure is not limited thereto.
The leak detecting device 1000 may calculate the total harmonic
distortion rate and a harmonic distortion factor based on the
voltage value for each harmonic component (S1106).
The total harmonic distortion rate may be calculated by Equation 3.
The harmonic distortion factor may be calculated by Equation 4. The
higher the total harmonic distortion rate and the harmonic
distortion factor, the more the harmonic components.
When the total harmonic distortion calculated by the leak detecting
device 1000 is less than a predetermined distortion rate, and when
the harmonic distortion factor is less than a predetermined
distortion rate, it may be determined that the harmonics less
influences the measured earth voltage. When it is determined that
the harmonics less influences the measured earth voltage, accuracy
and reliability may be increased, which may determine that the
earth voltage is generated by the leak of the AC commercial power
by calculating the effective value, the content rate, and the
zero-crossing count based on the measured earth voltage.
The leak detecting device 1000 may estimate the zero-crossing count
at which the earth voltage converted into the digital value passes
through zero voltage for a predetermined time T1 (S1106). Here, the
predetermined time T1 may be a time which is a predetermined
integer multiple of a cycle of the AC commercial power.
The leak detecting device 1000 may estimate the zero-crossing count
passing through the zero voltage when the polarity of the earth
voltage is changed for the predetermined time T1.
The zero-crossing count estimated by the leak detecting device 1000
may determine that the measured earth voltage contains more
fundamental frequency components, which are the power frequency of
the AC commercial power and the measured earth voltage is generated
by the leak of the AC commercial voltage.
For example, the predetermined time T1 may be set to 5 times of the
cycle of the AC commercial power. In this case, the zero-crossing
count of the AC commercial power is 10. When the zero-crossing
count of the measured earth voltage is 10, it may be determined
that the earth voltage contains more value of 60 Hz component, and
the measured earth voltage is generated by the leak of the AC
commercial voltage. On the contrary, when the zero-crossing count
of the measured earth voltage exceeds 10, it may be determined that
the earth voltage contains more frequency components more
significant than 60 Hz, and this is the earth voltage generated by
the influence of the harmonics or by the parasitic voltage.
Further, as described above, referring back to FIG. 7, the measured
earth voltage is similar to the 60 Hz waveform, which is the power
frequency. However, since the content rate is less than the
predetermined content rate (for example, 85%), it may be determined
that the earth voltage is generated by not the leak but the
parasitic voltage. Referring back to FIG. 8, in the case of the
measured earth voltage, the content rate exceeds the predetermined
content rate (e.g., 85%), but the waveform is not similar to the
waveform of 60 Hz which is the power frequency, and the
zero-crossing count of the AC commercial power exceeds the
zero-crossing count of the earth voltage for the predetermined time
T1 to determine that the corresponding voltage is the earth voltage
generated by not by the leak, but raised by the influence of the
harmonics or the parasitic voltage.
The method for determining that the earth voltage is generated by
the leak of the AC commercial voltage based on the zero-crossing
count is just an example, and the present disclosure is not limited
thereto.
The leak detecting device 1000 may estimate the distortion count,
which is the number of times the distortion by the harmonics occurs
in the measured earth voltage for the predetermined time T1
(S1108). Here, the predetermined time T1 may be a time which is a
predetermined integer multiple of a cycle of the AC commercial
power.
A specific method of estimating the number of distortions by the
leak detecting device 1000 will be described with reference to
FIGS. 31 and 32.
FIG. 31 illustrates an example for describing a method for
calculating the number of distortion times according to another
embodiment of the present disclosure.
Referring to FIG. 31, when the polarity of a first change amount of
a digital value of first earth voltage converted through sampling
and a digital value of second earth voltage converted through
sampling after a next sampling period and the polarity of a second
change amount of a digital value of the second earth voltage and a
digital value of third earth voltage converted through sampling
after a next sampling period are different from each other, the
leak detecting device 1000 determines that the distortion by the
harmonics occurs to estimate the distortion count. For example,
when the digital value of the first earth voltage is 50 mV and the
digital value of the second earth voltage sampled next is 53 mV,
the first change amount as (+)3 mV has a positive polarity. When
the digital value of the third earth voltage sampled next is 52 mV,
the second change amount as (-) 1 mV has a negative polarity. In
this case, the polarity of the first change amount and the polarity
of the second change amount are different from each other, and it
may be determined that the distortion by the harmonics occurs and
the distortion count may be estimated.
FIG. 32 is a flowchart for the method for calculating the number of
distortion times according to another embodiment of the present
disclosure.
Referring to FIG. 32, when the polarity of the first change amount
is different from the polarity of the second change amount, the
leak detecting device 1000 may estimate one time as the distortion
count. When the total distortion count estimated for the
predetermined time T1 is less than a predetermined distortion
count, it is determined that the harmonics fewer influences the
measured earth voltage. When it is determined that the harmonics
fewer influences the measured earth voltage, accuracy and
reliability may be increased, which may determine that the earth
voltage is generated by the leak of the AC commercial power by
calculating the effective value, the content rate, and the
zero-crossing count based on the measured earth voltage.
The leak detecting device 1000 may determine that the earth voltage
is generated by the leak of the AC commercial power based on at
least any one of the effective value of the earth voltage, the
voltage content rate, the total harmonic distortion, the harmonic
distortion factor, the zero-crossing count, and the distortion
count and determine a region where the earth voltage is measured as
the suspicious earth leaking area based on the determination
result.
The leak detecting device 1000 determines whether the effective
value of the earth voltage exceeds a predetermined threshold
voltage value (S1109).
When the effective value of the earth voltage exceeds the
predetermined threshold voltage value, the leak detecting device
1000 determines whether the voltage content rate exceeds a
predetermined voltage content rate (S1110).
When the voltage content rate exceeds the predetermined voltage
content rate, the leak detecting device 1000 determines whether the
total harmonic distortion is less than a predetermined total
harmonic distortion (S1111).
When the total harmonic distortion is less than the predetermined
total harmonic distortion, the leak detecting device 1000
determines whether the harmonic distortion factor is less than a
predetermined harmonic distortion factor (S1112).
When the harmonic distortion factor is less than the predetermined
harmonic distortion factor, the leak detecting device 1000
determines whether the zero-crossing count coincides with a
predetermined count (S1113).
When the zero-crossing count coincides with the predetermined
count, the leak detecting device 1000 determines whether the
distortion count is less than a predetermined count (S1114).
When the distortion count is less than the predetermined count, the
leak detecting device 1000 determines that the earth voltage is
generated by the leak of the AC commercial power (S1115).
The method for determining the suspicious earth leaking area is
just an example, and the present disclosure is not limited
thereto.
FIG. 36 is a flowchart for a method for determining a leak point
according to another embodiment of the present disclosure.
When it is determined that the earth voltage measured in the power
line PEN is generated by the leak of the AC commercial power, the
leak detecting device, 1000 may determine a point where the leak
occurs in the power line along a path of the power line buried in
the ground of the power line PEN where the earth voltage is
measured as the leak point.
First, the leak detecting device 1000 may receive the magnetic
field signal generated from the exploration current generating
device (S1201).
As described above, the exploration current generating device
injects the current signal into the power line and the neutral line
within the suspicious earth leaking area and the leak detecting
device 1000 may receive the magnetic field signal generated by
exploration current which flows on the power line and the neutral
line on the ground.
The leak detecting device 1000 may search the path of the power
line buried in the suspicious earth leaking area based on the
received magnetic field signal (S1202).
For example, the leak detecting device 1000 may determine a point
where the magnitude of the magnetic field signal is the maximum
point as a buried power line path. Further, the leak detecting
device 1000 may search a direction of a path in which the power
line is buried based on the magnetic field signal polarity.
First, the leak detecting device 1000 may receive the leak
detection voltage signal generated from the leak detection voltage
signal generating device (S1203).
As described above, the leak detection voltage signal generating
device transmits the leak detection voltage signal, which is DC
pulse voltage, to the power line. When the leak occurs in the power
line, the AC commercial power includes the leak detection voltage
signal to measure the earth voltage. The earth voltage measured by
the leak detecting device 1000 also includes a harmonic component
so that it is difficult to determine whether the pulse voltage
component is the leak detection voltage signal or the harmonic
component in the earth voltage. Therefore, the leak detection
voltage signal generating device transmits the leak detection
voltage signal after a predetermined time from the time when the
exploration current generating device transmits the exploration
current signal. Based on the time of receiving the magnetic field
signal generated by the received exploration current, the leak
detecting device 1000 may detect the pulse voltage component as the
leak detection voltage signal in the earth voltage measured after a
predetermined time.
First, the leak detecting device 1000 may set the logical value
according to whether to receive the leak detection voltage signal
(S1204).
The leak detecting device 1000 may determine whether the set
logical value and the logical value of the leak detection voltage
signal generated by the leak detection voltage signal generating
device coincide with each other (S1205).
When the set logical value and the logical value of the leak
detection voltage signal coincide with each other, the leak
detecting device 1000 may determine a point where the magnitude of
the leak detection voltage signal has the maximum value as the leak
point (S1206).
When the magnitude of the leak detection voltage signal has the
maximum value, the leak detecting device 1000 may determine a point
where the leak detection voltage signal is received as the leak
point (S1207).
It will be appreciated by those skilled in the art that information
and signals may be expressed by using various predetermined
technologies and techniques. For example, data, instructions,
commands, information, signals, bits, symbols, and chips, which may
be referred in the above description may be expressed by voltages,
currents, electromagnetic waves, magnetic fields or particles,
optical fields or particles, or predetermined combinations
thereof.
It may be appreciated by those skilled in the art that various
exemplary logical blocks, modules, processors, means, circuits, and
algorithm steps described in association with the embodiments
disclosed herein may be implemented by electronic hardware, various
types of programs or design codes (for easy description, herein,
designated as "software"), or a combination of all of them.
In order to clearly describe the inter compatibility of the
hardware and the software, various exemplary components, blocks,
modules, circuits, and steps have been generally described above in
association with functions thereof. Whether the functions are
implemented as the hardware or software depends on design
restrictions given to a specific application and an entire system.
Those skilled in the art of the present disclosure may implement
functions described by various methods with respect to each
specific application, but it should not be analyzed that the
implementation determination departs from the scope of the present
disclosure.
Further, various embodiments presented herein may be implemented as
manufactured articles using a method, a device, or standard
programming and/or engineering technique. The term "manufactured
article" includes a computer program, a carrier, or a medium that
is accessible by a predetermined computer-readable device. For
example, a computer-readable medium includes a magnetic storage
device (for example, a hard disk, a floppy disk, a magnetic strip,
or the like), an optical disk (for example, a CD, a DVD, or the
like), a smart card, and a flash memory device (for example, an
EEPROM, a card, a stick, a key drive, or the like), but is not
limited thereto. Further, various storage media presented herein
include one or more devices and/or other machine-readable media for
storing information. The term "machine-readable media" include a
wireless channel and various other media that can store, possess,
and/or transfer command(s) and/or data, but are not limited
thereto.
It will be appreciated that a specific order or a hierarchical
structure of steps in the presented processes is one example of
exemplary accesses. It will be appreciated that the specific order
or the hierarchical structure of the steps in the processes within
the scope of the present disclosure may be rearranged based on
design priorities. The appended method claims provide elements of
various steps in a sample order, but it does not mean that the
method claims are limited to the presented specific order or
hierarchical structure.
The description of the presented embodiments is provided so that
those skilled in the art of the present disclosure use or implement
the present disclosure. Various modifications of the embodiments
will be apparent to those skilled in the art, and general
principles defined herein can be applied to other embodiments
without departing from the scope of the present disclosure.
Therefore, the present disclosure is not limited to the embodiments
presented herein but should be analyzed within the widest range,
which is consistent with the principles and new features presented
herein.
* * * * *